1. Field of the Invention
The invention relates to a combined plant/heat pump circuit.
2. Related Technology
It is known in the state-of-the-art to employ refrigerant circuits for the combined use as a cooling plant and heat pump. Also for the use in motor vehicles such combined systems have gained in importance. This is due to the fact that modern engine designs for motor vehicles produce less and less waste heat, which up to now has been used to heat the passenger compartment. This results in not enough heat being available to provide sufficient heat for the passenger compartment. Therefore, a cooling unit already provided as air conditioning unit is, after modification, used as heat pump in order to exploit the air of the environment or the refrigerant circuit of the vehicle as heat source to heat the passenger compartment.
A combined system of a cooling plant and heat pump ensues from U.S. Pat. No. 5,375,424. For such a system, additional heat exchangers are needed which are integrated into the refrigerant circuit by means of a combination of multi-way valves.
A combined heat pump-cooling plant system for motor vehicles also ensues from U.S. Pat. No. 5,709,102. Here, a single external heat exchanger is combined with two series-connected interior heat exchangers and a switching valve.
Also, in U.S. Pat. No. 5,689,962 a combined system of heat pump and cooling plants is disclosed, but not for motor vehicle applications.
The systems know in the stat-of-the-art are characterized in that, when interior heat exchangers are used, there is the danger of condensation of the refrigerant in the interior heat exchanger during heat pump operation.